System and apparatus for reducing arcing and localized heating during microwave processing

ABSTRACT

A system and apparatus for reducing arcing and localized heating as a result of applying microwave energy to a microelectronic substrate having electronic components thereon is provided. A microwave furnace having a chamber is configured to secure a microelectronic substrate therewithin. The microelectronic substrate is electrically interconnected with a ground connected to an interior wall of the microwave furnace. A holder for securing a microelectronic substrate during the application of microwave energy and for providing the necessary electrical connections for grounding components and circuitry thereon is also provided. The holder may have a heat sink for protection against heat build-up and for maintaining a microelectronic substrate in a substantially flat orientation during microwave processing.

FIELD OF THE INVENTION

The present invention relates generally to microwave energy, and moreparticularly to reducing arcing and localized heating caused by theapplication of microwave energy.

BACKGROUND OF THE INVENTION

Assembling microelectronics often comprises mounting various electroniccomponents (e.g., transistors, capacitors, resistors, semi-conductorcomponents, etc.) on a microelectronic substrate (e.g., a rigid orflexible circuit board). Often, these substrates are, in turn, mountedon, or connected to, other components and devices. For various reasons,traditional mounting methods utilizing lead-based solder have becomeless desirable. Increasingly common now are the use of conductivepolymeric adhesives to mount electronic components on microelectronicsubstrates, and non-conductive polymeric adhesives to connect variouscomponents and devices.

In general, an uncured conductive adhesive is applied to amicroelectronic substrate so that, when placed within the adhesive, theelectronic component is connected to the underlying circuitry. After theelectronic component is placed in the adhesive, the adhesive is cured tosecurely connect the component to the substrate. Similarly, an uncurednon-conductive adhesive may be applied to a microelectronic substrate,the substrate placed on another component or device, and the adhesivecured to securely connect the substrate to the component.

Various methods of curing polymers are known. These methods typicallycomprise the application of heat by various techniques. Other methodsinclude the addition of curing agents, with or without heat. The generaluse of microwave irradiation is becoming more common. For example, U.S.Pat. No. 5,317,045 to Clark, Jr. et al., relates to a method of curing apolymeric material using microwave energy. The advantage of curingpolymeric resin with microwave energy is that the time required to cureis less than the time required using conventional methods. This isbecause the volumetric deposition of microwave energy is more efficientthan conduction from the surface resulting from conventional heatingtechniques. See, for example, Polymer Curing In A Variable FrequencyMicrowave Oven, R. J. Lauf et al., Oakridge National Laboratory. Seealso, U.S. Pat. No. 5,296,271 to Swirbel et al., which discloses amethod of curing photoreactive polymers by exposing them to microwaveenergy.

Unfortunately, when microwave energy is applied to a microelectronicsubstrate, arcing and/or rapid accumulation of heat may occur which maycause localized damage to the circuit board, to the component beingmounted to the circuit board, or to both. In general, metalliccomponents that are exposed to microwaves will arc or experienceexcessive heat accumulation unless grounded. Arcing results from thebuildup of a differential charge between different components or betweenone or more of the electronic components and the interior walls of themicrowave chamber. When the difference in potential exceeds theresistance of a dielectric medium, such as air, the result is a releaseof the built-up charge through the dielectric medium, physicallymanifested by an arc between two oppositely charged components.

Additionally, when microwave energy is applied to a microelectronicsubstrate comprising circuitry, localized heating of selected areas ofthe substrate may result. Selective portions of the conductive circuitrymay heat more rapidly than other portions, resulting in damage to thatportion of the circuitry. Furthermore, microelectronic components aretypically comprised of a plurality of materials, each of which mayrespond differently to the application of microwave energy. Somematerials may heat more rapidly than others, resulting in damage to thatportion of the component.

A microelectronic substrate may typically comprise a plurality ofmicroelectronic components bonded thereto using different polymers andresins. Because of the different types of materials comprising thecomponents, their different geometries, and their configuration relativeto one another, curing times may vary from one portion of the substrateto another. Unfortunately, the processing time for a substrate isdependent on the time required to cure the slowest component/resinconfiguration.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to reduce arcingresulting from microwave processing of microelectronic substrates.

It is another object of the present invention to reduce localizedheating resulting from microwave processing of microelectronicsubstrates.

It is yet another object of the present invention to provide improvedcuring times of conductive and non-conductive polymeric adhesivesthrough a combination of convection heating and microwave energy.

These and other objects are provided, according to the presentinvention, by a system and apparatus for microwave processing of amicroelectronic substrate which reduces arcing and localized heatingthat may occur when the substrate and components thereon are exposed tomicrowave energy. The system comprises a chamber including a microwaveenergy generator; securing means for holding a microelectronic substratewithin the chamber; and electrical means for electricallyinterconnecting the microelectronic substrate with an interior wall ofthe microwave chamber so as to ground the substrate and componentsthereon. The apparatus comprises a holder for securing a microelectronicsubstrate during the application of microwave energy, for providing thenecessary electrical connections for grounding the microelectronicsubstrate and components contained thereon, and for alleviating thelocalized accumulation of heat during microwave processing.

In particular, the holder comprises a substantiallymicrowave-transparent base to which a microelectronic substrate can beremovably secured for microwave processing. Acceptablemicrowave-transparent materials include ceramics, such as fibrouszirconia, and compositions of silica and alumina. Also acceptable arepolymers, including polyethylene, polyamide, and TEFLON® (E. I. DuPontde Nemours Company, Wilmington, Del.). The base includes at least oneinternal bore sized and configured to receive an electrical conductor.The electrical conductor extending through the bore has a substrate endconfigured to electrically interconnect the microelectronic substrateand a ground end configured to electrically interconnect with one of theinterior walls of the microwave chamber. The bore terminates at asubstrate end located to facilitate the connection of the conductorsubstrate end with the microelectronic substrate. The bore alsoterminates at a ground end opposite the substrate end to facilitate theconnection of the conductor ground end with one of the interior walls ofthe microwave chamber.

The holder may be configured to secure a plurality of microelectronicsubstrates, wherein a plurality of internal bores having a plurality ofelectrical conductors extending through a respective one of the internalbores are provided. Each one of the plurality of electrical conductorshas a substrate end configured to electrically interconnect with arespective microelectronic substrate and a ground end configured toelectrically interconnect with one of the interior walls of themicrowave chamber.

According to another aspect of the invention, a microwave-absorbent massis positioned on the base so that a predetermined portion of themicroelectronic substrate overlies the mass when the microelectronicsubstrate is secured to the base. Acceptable materials for themicrowave-absorbent mass include silicon carbide, ferric oxide, carbonblack, copper oxide black and metals in powdered form, such as silverand aluminum. A plurality of microwave-absorbent masses may bepositioned on the base so that a respective predetermined portion of themicroelectronic substrate overlies each mass when the microelectronicsubstrate is secured to the base. When microwave energy is applied, themicrowave-absorbent mass heats rapidly and produces localized convectiveheating. Consequently, the cure rate of a polymer located near amicrowave-absorbent mass can be increased as a result of the combinationof microwave energy and convective heating.

According to another aspect of the invention, a pin having a tip extendsfrom the base so that the tip is in adjacent relationship with apredetermined portion of the microelectronic substrate when themicroelectronic substrate is secured to the base. The tip has a groundend opposite from the tip and electrically interconnected with anelectrical conductor extending through an internal bore. When the baseis subjected to microwave energy, the microwave field is intensified atthe tip. Consequently, the cure rate of a polymer located near the tipcan be increased as a result of the intensified microwave energy.

A base may further comprise a plurality of pins each of which has a tipand extends from the base so that each tip is in adjacent relationshipto a respective predetermined portion of the microelectronic substratewhen the microelectronic substrate is secured to said base. Each pinalso has a ground end opposite from the tip, electrically interconnectedwith an electrical conductor extending through an internal bore.

According to another aspect of the invention, the holder may comprise aheat sink designed to protect selective portions of a microelectronicsubstrate, including components and circuitry thereon, from excessiveheat build-up. The heat sink is positioned directly above, and incontact with, the portion of the microelectronic substrate to beprotected and is designed to absorb heat caused by microwave processing.The heat sink is comprised of a substantially microwave-transparentmaterial, similar to the base of the holder and has a high specificheat. Because the heat sink material has a high specific heat, heat atthe point of contact with the substrate is absorbed by the heat sink. Anadditional advantage of the heat sink is that it facilitates maintainingan underlying substrate in a substantially flat orientation duringmicrowave processing.

According to another aspect of the invention, a system and apparatus isprovided for microwave processing of a workpiece which reduces arcingand localized heating that may occur when the workpiece and anycomponents thereon or therein are exposed to microwave energy. The term"workpiece" is used hereinafter to refer to any object that is exposedto microwave irradiation processing, including, but not limited to,electronic components and substrates (including microelectroniccomponents and substrates). The system comprises a chamber including amicrowave energy generator; securing means for holding a workpiecewithin the chamber; and electrical means for electricallyinterconnecting the workpiece with an interior wall of the microwavechamber so as to ground the workpiece and components thereon. Theapparatus comprises a holder for securing a workpiece during theapplication of microwave energy, for providing the necessary electricalconnections for grounding the workpiece and components containedthereon, and for alleviating the localized accumulation of heat duringmicrowave processing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a system and apparatus for reducingarcing and localized heating during microwave processing, according tothe present invention.

FIG. 2 is a perspective view of a holder assembly, according to thepresent invention.

FIG. 3 is an exploded perspective view of the holder assembly of FIG. 2.

FIG. 4 is a sectional view taken along lines 4--4 in FIG. 2.

FIG. 5 is a perspective view of another embodiment for reducing arcingand localized heating during microwave processing of a flexiblesubstrate, according to the present invention.

FIG. 6 is a perspective view of a heat sink, according to the presentinvention.

FIG. 7 is a section view of the heat sink taken along lines 7--7 in FIG.6.

FIGS. 8-11 illustrate the use of microwave-absorbent materials in theholder assembly, according to the present invention.

FIGS. 12-13 illustrate the use of pins in the holder assembly forintensifying microwave energy, according to the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention now is described more fully hereinafter withreference to the accompanying drawings, in which preferred embodimentsof the invention are shown. This invention may, however, be embodied inmany different forms and should not be construed as limited to theembodiments set forth herein; rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey the scope of the invention to those skilled in the art. In thedrawings, the thickness of layers and regions may be exaggerated forclarity. Like numbers refer to like elements throughout.

Referring now to FIGS. 1-4, a system for reducing arcing and localizedheating during microwave processing of a microelectronic substrateaccording to the present invention is illustrated. The system 10comprises a microwave furnace 11 having a chamber 12 defined by aplurality of walls 13; a ground 14 connected to at least one of theinterior walls of the microwave chamber; a holder assembly 20 forremovably securing a flexible or rigid microelectronic substrate 23having a plurality of microelectronic components 24 thereon; and aplurality of electrical conductors 30, 30' for connecting themicroelectronic substrate 23 to the ground 14. A particularly preferredmicrowave furnace is described in U.S. Pat. No. 5,321,222, to Bible etal., the disclosure of which is incorporated herein by reference in itsentirety.

The present invention is not limited to microwave processing ofelectronic components and substrates, but is applicable to any and allobjects (or "workpieces" as described above) that may be exposed tomicrowave irradiation processing. The system and apparatus disclosedherein may be used to reduce arcing and localized heating that may occurwhen the workpiece and any components thereon or therein are exposed tomicrowave energy.

The holder assembly 20 comprises a substantially microwave-transparentbase 21 having a surface 22 for removably receiving and securing amicroelectronic substrate 23. The base 21 may include at least oneinternal bore 25 sized and configured to receive at least one electricalgrounding conductor 30 therethrough. The internal bore 25 terminates attwo openings: a substrate end opening 25a in the surface 22 upon whichthe microelectronic substrate 23 is secured, and a ground end opening25b in another portion of the base 21. As illustrated in FIG. 3, thebase 21 may comprise a plurality of internal bores 25, substrate endopenings 25a, and ground end openings 25b.

The internal bore 25 in the base 21 is preferably sized and configuredto receive a flat, flexible electrical conductor 30. The flexibleelectrical conductor 30 extends through the internal bore 25 andpreferably has a substrate end 34 configured to electricallyinterconnect with the microelectronic substrate through the substrateend opening 25a. At the opposite end of the electrical conductor 30, aground end 35 is preferably configured to electrically interconnect witheither an additional electrical conductor 30' (FIGS. 1-4) or, as shownin FIG. 5, directly with a ground 14. Preferably, the electricalconductors 30, 30' each comprise a plurality of metallic wires wrappedin a polymeric dielectric material, such as polyamide, adapted at eachend to receive various types of connectors 31. However, as would beunderstood by those having skill in the art, a conductor comprisingnon-metallic conductive material, such as screen-printed conductive inksand the like, would also be acceptable. Furthermore, the electricalconductors 30, 30' may each comprise only a single conductive pathway,such as a single wire or single conductive strip of material.

Preferably, the microelectronic substrate 23 is secured within arecessed portion 32 of the base 21. However, as would be understood bythose having skill in the art, the base 21 may have any desirable shapeand configuration for receiving a microelectronic substrate 23,including having no recessed portion 32, or by having a raised portion(not shown). Additionally, the microelectronic substrate 23 may beremovably secured to the base 21 by retaining clips, screws, tape, orother methods known to those having skill in the art. As discussedfurther below, a flexible microelectronic substrate 23, may be securedto the base 21 and maintained in a substantially flat orientation duringmicrowave processing by positioning a heat sink over the substrate.

Preferably, the base 21 is custom designed and machined for receiving aparticular microelectronic substrate 23. The base 21 is preferably madefrom machinable microwave-transparent materials such as ceramics andpolymers. Examples of ceramic material particularly suitable for thebase 21 include, but are not limited to, fibrous zirconia, andcompositions of silica and alumina. Particularly preferable are porouscompositions of silica and alumina having proportions of about 80%alumina and about 20% silica. Examples of polymeric materialparticularly suitable for the base 21 include, but are not limited to,Teflon®, polyethylene, and polyamide.

Referring to FIG. 4, substrate end openings 25a are located within thebase 21 at predetermined locations in order to properly align with aparticular microelectronic substrate 23. At each of the substrate endopenings 25a of the internal bores 25, a connector 31 is positioned inclose proximity to the recessed area 32 for receiving respectiveconnecting pins (not shown) extending from the microelectronic substrate23. The connectors 31 are provided to electrically interconnectcomponents 24 and portions of the microelectronic substrate 23 to beprotected from arcing and localized heating to a ground 14 via theelectrical conductors 30, 30'.

Referring to FIG. 3 a microelectronic substrate 23 having a plurality ofmicroelectronic components 24 is illustrated. Securing a microelectroniccomponent 24 to a microelectronic substrate 23 comprises applying acurable resin 41 to the substrate via an applicator 40, setting theconnecting pins 28 of the component in the resin, and curing the resin.As would be understood by those having skill in the art, amicroelectronic substrate 23 is a dielectric material having electroniccircuitry 26 thereon, to which various microelectronic components 24 arephysically and electrically connected. The circuitry 26 on themicroelectronic substrate 23 may be screen printed using conductivematerials, or may be applied to the substrate by other methods known tothose with skill in the art. The microelectronic substrate 23 may bemade from flexible or rigid materials. The resin 41 may be conductive ornon-conductive depending on the component and where on the circuitry thecomponent is located.

As would be well known to those having skill in the art, traditionalmethods for mechanically and electrically securing electrical componentsto circuitry comprised the use of solder. Electrical connecting pinsextending from a component were inserted into selective portions of acircuit on an electronic substrate and secured thereto by applyingmolten solder to the junction of the contact and circuit and allowing itto cool, and thereby harden. According to the present invention, bothelectrically conductive and non-conductive resins 41 are replacingsolder and other traditional methods of securing components to acircuit. The resin 41 is applied to various portions of the circuitwhere each connecting pin 28 of a component 24 is desired to connect tothe circuitry 26. The resin 41 serves to physically secure the component24 to the substrate 23 and to electrically connect the component to thecircuitry 26. Additionally, a non-conductive resin may be used to securevarious components to a microelectronic substrate, or to each other,where electrical conductivity is not needed or provided in some otherway. Conductive and non-conductive resins may also be used to secure themicroelectronic substrate to other objects.

Still referring to FIG. 3, the process of securing microelectroniccomponents 24 to a substrate 23, according to the present invention, maybe performed by hand or by automated equipment, typically inassembly-line fashion, and preferably under computer control. Automatedapplicators 40 may apply resin 41 to predetermined locations of aparticular microelectronic substrate 23. Electronic components 24 maythen be inserted within the resin by automated equipment. The substratemay then be forwarded to a microwave furnace for curing. Furthermore,the process of securing electronic components to a substrate, accordingto the present invention, may be part of larger process including thefabrication of the microelectronic substrate and circuitry.

Preferably, each component 24 to be grounded, and each circuit 26 to begrounded has one or more connecting pins or conductors, as required,extending from the microelectronic substrate 23. When themicroelectronic substrate 23 is placed on the holder assembly 20, theconnecting pins or conductors align with the connectors 31 so that anelectrical connection is made between the components 24 or circuit 26and the ground 14 (FIGS. 3 and 4). As would be understood by thosehaving skill in the art, other ways of electrically connecting acomponent 24 or portions of a circuit 26 to ground 14 may be utilized.For example, a conductor having one end connected to ground 14 may bedirectly attached at the other end to a component 24 or circuit 26 viaan alligator clip or similar device.

An electrical conductor 30 extends from connector 31 through internalbore 25 to a connector 42 located within the ground end opening 25b ofthe internal bore. As would be understood by those having skill in theart, electrical conductor 30 may extend further and connect to theground 14, or may terminate at connector 42 as illustrated in FIG. 4. Asillustrated, an additional electrical conductor 30' may extend fromconnector 42 to a ground 14. In the illustrated embodiment, a pluralityof conductors 30 extend through a plurality of internal bores 25 in thebase 21 and connect to a ground 14 via a plurality of additionalconductors 30'.

As would be known to those having skill in the art, microelectronicsubstrates are often manufactured with a flexible tail 44 as illustratedin FIG. 5. This configuration of substrate 23 and tail 44 permits thesubstrate, and components 24 thereon, to be protected from arcing andlocalized heating without requiring a holder assembly and withoutrequiring additional electrical conductors for grounding. Afterprocessing within the microwave furnace 11, the tail 44 may or may notbe cut, as indicated in FIG. 5, and removed from the microelectronicsubstrate 23.

In the illustrated embodiment a microelectronic substrate 23 includes aflexible tail 44 having a plurality of conductive leads 45 extendingfrom the circuitry 26 on the substrate. The tail 44 has an end portion46 which is connected to the ground 14 via the connector 47. Because ofits flexibility and length, the tail 44 can be grounded to any one ofthe interior walls 13 of the microwave chamber 12. A separate conductor(not shown) may also be utilized to ground the tail 44 without requiringa connector 47. For example, a conductor having one end connected toground 14 may be directly attached at the other end to a component 24 orcircuit 26 via an alligator clip or similar device. Additionally, aplurality of microelectronic substrates 23 having flexible tails 44 canbe processed simultaneously within the microwave furnace 11.

Referring now to FIGS. 6-7, the holder assembly 20 may also comprise aheat sink 52 for protecting portions of the microelectronic substrate23, including components 24 and circuitry 26 thereon, from the build-upof heat. The heat sink 52 is positioned directly above, and in contactwith, the portion of the microelectronic substrate 23 to be protectedand is designed to absorb heat caused by microwave processing. Becausethe heat sink material has a high specific heat, heat at the point ofcontact with the substrate 23 is absorbed by the heat sink 52. The heatsink 52 is preferably made from machinable microwave-transparentmaterials such as ceramics and polymers. Examples of ceramic materialparticularly suitable for the heat sink 52 include, but are not limitedto, fibrous zirconia, and compositions of silica and alumina.Particularly preferable are porous compositions of silica and aluminahaving proportions of about 80% alumina and about 20% silica. Examplesof polymeric material particularly suitable for the heat sink 52include, but are not limited to, Teflon®, polyethylene, and polyamide.

An additional advantage of the heat sink 52 is that it maintains anunderlying substrate 23 in a substantially flat orientation duringmicrowave processing. This is especially important when flexiblemicroelectronic substrates are being processed, because any flexing orbending during processing may result in a component not being adequatelymounted, or may exacerbate existing stresses caused by differentcoefficients of thermal expansion of the various connected materials.Furthermore, when a flexible microelectronic substrate is mounted toanother object, any flexing or bending during processing that becomespermanent after the resin has cured may result in the microelectronicsubstrate malfunctioning. The heat sink 52 may be an integral part ofthe holder assembly 20, or it may be a separate assembly used inconjunction with the holder assembly. Furthermore, the heat sink 52 maybe designed to protect a specific microelectronic substrate 23 or aportion thereof.

Referring back to FIG. 5, a heat sink 52 may also be placed on top of amicroelectronic substrate 23 that is being processed without a holder20. Also, as would be known by those having skill in the art, themicroelectronic substrate 23 may include a dielectric layer 48 overlyingportions of the circuitry 26 thereon. The dielectric layer 48 may servethe function of a heat sink to protect underlying portions of themicroelectronic substrate 23 from the build-up of heat. The dielectriclayer 48 is typically applied to the microelectronic substrate 23 duringmanufacturing of the substrate and can be placed thereon to selectivelyprotect portions of the circuitry 26.

According to another embodiment of the present invention, as illustratedin FIGS. 8-11, the recessed area 32 in the base 21 has grooves 49positioned to correspond with a plurality of predetermined locations onthe microelectronic substrate 23 when the substrate is placed on thebase. Within each of these grooves 49 is placed a highly conductivemicrowave absorbing material 50. As would be known to those having skillin the art, suitable highly conductive microwave absorbing materialsinclude, but are not limited to, silicon carbide, ferric oxide, carbonblack, and metals in powdered form.

When a microelectronic substrate 23 is placed on the base 21, andmicrowave energy is applied, the microwave absorbing material 50 withineach groove 49 heats to a predetermined temperature and suppliesadditional convective heating to a localized area of the microelectronicsubstrate above the microwave absorbing material. The resin 41 containedon the microelectronic substrate 23 directly above the microwaveabsorbing material is, thus, exposed to both microwave energy andconvective heating. As a result, polymers which do not cure as rapidlyas other polymers when subjected to a particular frequency of microwaveenergy, can be forced to cure faster by the combination of convectiveheating and microwave energy. Thus, in addition to providing thenecessary grounding as discussed above, the base 21 may also provide away to selectively increase the cure rate of polymers that is notachievable with microwave energy alone.

A holder assembly 20 having microwave absorbing materials 50 may becustom designed to fit a specific microelectronic substrate 23. In theillustrated embodiment, the grooves 49 are located within the recessedportion 32. However, as those skilled in the art would understand, thegrooves 49 within which the microwave absorbing material 50 is placedmay be located on the base 21 at any desirable position, including thesurface 22, and any raised portion (not shown) of the base.Alternatively, the microwave absorbing material 50 may be placeddirectly on the base 21 without requiring grooves. In addition, a heatsink 52 (FIG. 6), as described fully above, may be utilized with theembodiment of the present invention illustrated in FIGS. 8-11 in orderto protect portions of the microelectronic substrate 23, includingcomponents 24 and circuitry 26 thereon, from heat build-up.

According to another embodiment of the present invention, illustrated inFIGS. 12-13, the rate of cure of certain polymers and resins can beincreased by intensifying the microwave energy at specific locationsbeneath the microelectronic substrate 23. The base 21 may comprise aplurality of pins 60 each having a tip 60a extending from the base 21 sothat the tip is in adjacent relationship with a predetermined portion ofthe overlying microelectronic substrate 23 when placed on the base 21.Preferably the pins 60 point in the direction of the resin 41 to becured on the overlying substrate 23. The tip 60a of each pin 60 ispreferably in close proximity to the overlying microelectronic substrate23.

In the illustrated embodiment, each pin 60 extends from the base 21within a groove 49. However, each pin 60 may extend directly from thebase 21 without requiring a groove. Each pin 60 has a ground end 60bopposite from the tip 60a and is electrically connected with a groundedelectrical conductor 30 to reduce the possibility of arcing between thepin and other objects, including the microelectronic substrate 23,electronic components 24 on the substrate, the electronic circuitry 26,and the microwave chamber walls 13. The electrical conductor 30, towhich each pin 60 is electrically connected, preferably extends throughan internal bore 25 of the base 21. In addition, a heat sink 52 (FIG.6), as described fully above, may be utilized with the embodiment of thepresent invention illustrated in FIGS. 12-13 in order to protectportions of the microelectronic substrate 23, including components 24and circuitry 26 thereon, from heat build-up.

Each pin 60 is preferably made from a metallic material including, butnot limited to, silver, aluminum, and stainless steel. When each pin 60is subjected to microwave energy, the microwave field is intensified atthe tip 60a of the pin, which in turn leads to an increasedconcentration of microwave energy. The result is an increase in the rateof curing of the resin 41 located directly above each pin 60 on theoverlying microelectronic substrate 23.

In the drawings and specification, there have been disclosed typicalpreferred embodiments of the invention and, although specific terms areemployed, they are used in a generic and descriptive sense only and notfor purposes of limitation, the scope of the invention being set forthin the following claims.

That which is claimed:
 1. A system for reducing arcing and localizedheating during microwave processing of a microelectronic substrate, saidsystem comprising:a chamber including means for generating microwaveenergy; a substantially microwave-transparent base for removablysecuring the microelectronic substrate thereto, said base including atleast one internal bore sized and configured to receive an electricalconductor, said bore having a substrate end located to provide theelectrical conductor to the microelectronic substrate, and a ground endopposite the substrate end for providing the electrical conductor toground; and an electrical conductor having a substrate end configured toelectrically interconnect the microelectronic substrate and a ground endconfigured to electrically interconnect with a ground connected to saidchamber.
 2. A system according to claim 1, wherein said base furthercomprises a plurality of internal bores and a plurality of electricalconductors, each extending through a respective one of said plurality ofinternal bores and having a substrate end configured to electricallyinterconnect with the microelectronic substrate and a ground endconfigured to electrically interconnect with a ground.
 3. A systemaccording to claim 1, wherein said base is formed of ceramic material.4. A system according to claim 1, wherein said base is formed of polymermaterial.
 5. A system according to claim 1, wherein said base isconfigured to removably secure a plurality of microelectronicsubstrates.
 6. A system according to claim 1, further comprising atleast one heat sink for overlying selective portions of at least onemicroelectronic substrate secured within said chamber.
 7. A system forreducing arcing and localized heating during microwave processing of aworkpiece, said system comprising:a chamber including means forgenerating microwave energy; a substantially microwave-transparent basefor removably securing the workpiece thereto, said base including atleast one internal bore sized and configured to receive an electricalconductor, said bore having a workpiece end located to provide theelectrical conductor to the workpiece, and a ground end opposite theworkpiece end for providing the electrical conductor to ground; and anelectrical conductor having a workpiece end configured to electricallyinterconnect the workpiece and a ground end configured to electricallyinterconnect with a ground connected to said chamber.
 8. A systemaccording to claim 7, wherein said base further comprises a plurality ofinternal bores and a plurality of electrical conductors, each extendingthrough a respective one of said plurality of internal bores and havinga workpiece end configured to electrically interconnect with theworkpiece and a ground end configured to electrically interconnect witha ground.
 9. A system according to claim 7, wherein said base is formedof ceramic material.
 10. A system according to claim 7, wherein saidbase is formed of polymer material.
 11. A system according to claim 7,wherein said base is configured to removably secure a plurality ofworkpieces.
 12. A system according to claim 1, further comprising atleast one heat sink for overlying selective portions of at least oneworkpiece secured within said chamber.
 13. A system according to claim7, wherein said base further comprises a microwave-absorbent masspositioned on said base so that a predetermined portion of the workpieceoverlies said mass when the workpiece is secured to said base.
 14. Asystem according to claim 7, wherein said base further comprises a pinhaving a tip and extending from said base so that said tip is inadjacent relationship to a predetermined portion of the workpiece whenthe workpiece is secured to said base, and a ground end opposite fromsaid tip, electrically interconnected with the electrical conductor.